The body of a person suffering from diabetes is not able to produce a sufficient quantity of insulin, or it does not react in an appropriate way to the insulin it produces. This fact results in an imbalance in the glucose concentration in the blood (that is to say in hyperglycaemia or hypoglycaemia) which may be the cause of serious consequences, such as ketoacidosis, complications in the blood vessels, spasms or loss of consciousness. To maintain a healthy blood glucose level (also known as blood sugar level), diabetic patients usually follow strict diets and combine these with a basal insulin release and with selective insulin boluses. In this case, the insulin release needs to be individually tailored to the patient's body in order to provide it with the correct amount of insulin at the correct time. To determine the time and amount of the next insulin bolus, patients regularly measure the glucose concentration in their blood and determine the carbohydrate content of their meals.
Instead of taking blood glucose measurements using strip meters, which, depending on the intensity of the therapy being carried out, happens three to six and only in exceptional cases, ten or more times per day, it is possible to use continuously operating blood glucose meters. One of the advantages of a continuously operating measurement system is the facility to calculate trend information, which can only be done usefully with a high rate of measured data. In this case, the calculated trend information usually relates to the values measured beforehand and therefore provides information about the profile of the glucose concentration in the near future. External influences such as the administration of an insulin bolus, the taking of meals or sports activities influence the accuracy of the trend information. Supplying a measurement system with information about these external influences can significantly increase the accuracy of the trend calculation and therefore particularly also allows the dosage of an insulin bolus to be matched more accurately to the needs of a patient.
Blood glucose meters for continuously collecting glucose data are usually portable. Data stores for storing the captured data account for a significant proportion of the appliance costs in the case of such appliances. With the currently usual sampling intervals of five minutes, for example, a large volume of data is already produced which cannot be effectively compressed using conventional data compression without losing valuable information. In addition, by way of example, retrospective trend calculation with sufficient accuracy for the further data evaluation is possible only with difficulty, even at five-minute storage intervals, particularly if the stored signal is additionally overlaid with noise.